Stroboscopic apparatus



Feb. 4, 193,0.

A. (J. ASHDQWN STROBOSCOPI C APPARATUS Filed May 28, 1921 JNVENVTOR.

MAm m MM A M A period and area ofvision thefrequency of*observation Vwas increased one would obtain better results, and my invention broadlyp 40 characterized in that in stroboscoplc appara I quency ofobservation is not'thesameas I LB RT JAsrna As nowN, or LETCHWOBTI-I,ENGLAND smdres AIPABATUSI i Application niece/ ray 2s,

7 My invention relates tofstroboscopiclapprovements in nomena inparatus, and has for its object to provide im-j such apparatus-whichwill enc able an e'asy and accurate stu'dyof manyphef machine shop andlike work, the nature of-which previously has been largely a' matterofassumption. 5 I In existing stroboscopic apparatus,theshutter mechanismissuch that the length of each period the object being viewed is under.ob-

servation hasat all times a constant unalterablerelationship to theeclipse period. For

example, if it is desired to'obtain greater definition ofthe objectbeing observedthe opera-.

tor would probably endeavour to shorten the time of each observationperiod by increasing the speed oftheshutter. This however,willnecessarily also reduce the time ofthe eclipse periodto aproportional extent, whereas the observer would most probably want toreduce I the observation period without altering the eclipseperiod. Infact it is found that they 7 "present forms of shutters haveundesirableb they fact that the rate of travelof the limitations because of theeclipse and observation periods being so intimately, relatfid that it isimpossible to achieve the deside-ratum of exceedinglyshort observationperiods inrelation to the eclipse periods. This is due to aperturedportion of the shutter mechanism travel or the, speed factor of. the oneis different to the other, more particularly so as to ensure that for agiven length of observation tus the speed factor determining-the frethatwhich determined the'lengthoftime of each observation.

p In the preferredembodiment of my invention the speed of that part or"the apparatus which determines the length of" time of each observationis a suitable 'multi-.

ple such as nine times that 'o fjthe part of the apparatus whichdetermines "the: frequency of'observation. According to the preferredembodiment of is ex-. actly the same as the part not apertured," whereasif one could arrange that therate of 1927; Serial No. 195,965, and inGreat Britain June 3, 1926.

invention eniploy instead of only one Y shutter, a pair of shuttersarranged across the line of vision, both v movingsimultaneouslyandpreferably in the same direction and the speed of one being greaterthan the speed of r Pic E the other. i I can employ for this purpose a Ypairof concentric sleeve-like shutters, both apertured so that all ofthe apertures canat intervals coincide on a common line of vision, theinner shutter however belng rotated at an appreciably lesser speed thanthe outer jshutter. 'In this event, the innershutter wouldofcourse'determine thefr'equency of observation,'and the outer shutterwould determine the length of time of each observation.

In order that the present invention can be I clearly understooda'ndreadily carried into efie'ct, Ihaveappended hereto I a sheet of drawingsillustrating twol embodimentsf'of same, andwhereinz i v ig. 1-is anoutside elevation of ashutterc ompos'ed' o f two concentric cylindersor,thej other determines thejduration of each] pei'lod c VlSlOIl. Forthl'spurpose two shuts te r's, are: rotated at ,diiierent' relative speeds,

theslower moving shutter a (Figs.'l ,to controlling the period orfrequency of the vision whilst the second more rapidly moving shutter b(Figsl to 4) decides the-duration oteac'h periodic vision. These twoshutters may; be driven independently with separate speed controls ormay be, interconnected by suitable gearin'g'so-that they move atdifierent relative speeds. A suitable form of gearing -0 may be arrangedbetween the shutters or between' them and the driving means'to enableany suit-ablecombination of speeds to beobtained' The shutters wand '19are cylindricalf and adapted to rotate about a I j;

common axis preferably the same direction, but if deslred 1n the reversedlrectl'ons;

The shutter a is disposed concentrically outside the shutter Z) and theshutters are provided with apertures a and 6 preferably of an elongatedslot form situated opposite to each other. One shutter may be rotatedthrough an electric motor or by hand or mechanical means either directlyor through suitable gearing so that a suitablev speed of rotation Willbe obtained to provide the desired period or frequency of VlSlOll forany particular obj ectwhich may be under observation. The other shutteris driven in a similar manner either through a 'separate motor andgearing or by a geared connection to the first shutter at a higher speedas shown by the gearing c in Figs. 1 and 2. The inner shutter 6 controlsthe duration of each vision, and the outer shutter a determines thefrequency of vision. The vision of the object will occur each time theapertures a in the outerand slower moving cylinder at are op-* thosenecessary to give the desired stationary or slow moving vision oftheobject under examination, that is to say twice every revolution ofthe outer shutter there will be a vision period, but each such visionperiod would only occur once during a number of revolutions of the innershutter b. The relative high rate of movement of the inner shu'tter bwill ensure sharp definition of the object. If desired the slotted orother apertures in the cylinder 25 and/or in the cylinder a may becompounded or divided into a number of narrow apertures by means oflongitudinal fiat strips 0! (see Fig. 4) arranged preferably parallel tothe line of vision through the centre of the aperture; Whilst suchanarrangement might apply to a limited extent to both shutters it isprimarily intended for use in the inner shutter Z) onlyand is adapted togive an exceedingly'rapid opening and closing of the shutter with acomparatively large effective aperture thus enabling high definition tobe'obtained without excessive speeds.

The gearing 0 can be driven from any suitable source, and the primaryrotary memher in each such gearingconsists of a relatively largediameter wheel meshing with a small gear wheel Z fixed on the spindle mof the inner cylinder 6 to which the fast move 7 ing disc 6 is secured,the wheel is carrying with 1t a smaller gear wheel n meshing with a gearwheel 0 secured tov the outer cylinder a.

respectively, 7

I claim 1. Stroboscopic apparatus including a rotary cylindricalshutter, a second rotary cy lindrical shutter concentric with said firstshutter, diametrically opposed apertures in said first mentionedshutter, diametrically opposed aperturesin said second mentioned shuttermovable across said first mentioned apertures and means for driving saidfirst and second shutters at different speeds.

2. :Stroboscopic apparatus according to claim 1 including gearingoperatively connectedbetween said first and second shutters.

LBERT JASPER ASHDQWN.

